We must humble ourselves before our God because we said in our hearts that we must be humble before Him.
Remember that the Bible itself speaks of people who were haughty and very proud, and God does not like these things in people’s lives.
6 Though the Lord be high, yet hath he respect unto the lowly: but the proud he knoweth afar off.
7 Though I walk in the midst of trouble, thou wilt revive me: thou shalt stretch forth thine hand against the wrath of mine enemies, and thy right hand shall save me.
8 The Lord will perfect that which concerneth me: thy mercy, O Lord, endureth for ever: forsake not the works of thine own hands.
Psalm 138:6-8 (KJV)